Pifithrin-α (PFT-α; ) is a reversible inhibitor of p53-dependent transcription and apoptosis. Cyclic PFT-α, also known as PFT-β, is a stable analog of PFT-α, formed by the condensation of pifithrin-α in solution. It inhibits the growth of the cancer cell lines IGROV-1, A2780, and HCT116 (IC50 = 23, 77, and 103 μM, respectively). At doses lower than those that inhibit growth, cyclic PFT-α induces autophagy in HCT116 cells and sensitizes IGROV-1 and H460 cells to anti-microtubule agents. In addition, 10 μM cyclic PFT-α blocks p53-dependent protection from DNA damage, induced by hydrogen peroxide or ultraviolet radiation, in melanocytes.
